Sugar poses enough health risks that it should be considered a controlled substance just like alcohol and tobacco, contend a team of researchers from the University of California, San Francisco (UCSF).In an opinion piece called "The Toxic Truth About Sugar" that was published Feb. 1 in the journal Nature, Robert Lustig, Laura Schmidt and Claire Brindis argue that it's a misnomer to consider sugar just "empty calories." They write: "There is nothing empty about these calories. A growing body of scientific evidence is showing that fructose can trigger processes that lead to liver toxicity and a host of other chronic diseases. A little is not a problem, but a lot kills - slowly."Almost everyone's heard of - or personally experienced - the proverbial sugar high, so perhaps the comparison between sugar and alcohol or tobacco shouldn't come as a surprise. But it's doubtful that Americans will look favorably upon regulating their favorite vice. We're a nation that's sweet on sugar: the average U.S. adult downs 22 teaspoons of sugar a day, according to the American Heart Association, and surveys have found that teens swallow 34 teaspoons.To counter our consumption, the authors advocate taxing sugary foods and controlling sales to kids under 17. Already, 17% of U.S. children and teens are obese, and across the world the sugar intake has tripled in the past 50 years. The increase has helped create a global obesity pandemic that contributes to 35 million annual deaths worldwide from noninfectious diseases including diabetes, heart disease and cancer."There are good calories and bad calories, just as there are good fats and bad fats, good amino acids and bad amino acids, good carbohydrates and bad carbohydrates," Lustig, a professor of pediatrics and director of the Weight Assessment for Teen and Child Health (WATCH) program at UCSF, said in a statement. "But sugar is toxic beyond its calories."